The Jazz didn't make this pick in a vacuum. They must have considered all kinds of factors. One consideration may be that the Jazz could lose either Exum or Rubio within a year due to free agency, so they want a guy who can play PG in that eventuality, while also being versatile enough to play the 2 as well. Maybe the Jazz think they're going to be able to get a forward who can score via free agency, so taking Hutchison or Jacob Evans weren't priorities. The Jazz are very focused on maximizing the next 2 - 3-year window and may not have had the patience or the roster flexibility to develop a player like Simons.
That said, at face value Hutchison, Simons and Okobo all look like better talents than Allen, imo.
Allen is a 4-year college player, very well coached. He's a guy who obviously looks good in workouts. His best position longer term may actually be at the 1 where he has a size and strength advantage. It sounds like he dominated against Jalen Brunson in his Jazz workout. My criticisms of him are that he can't really get by defenders off the dribble, he's mediocre at creating looks for himself, and he'll be yet another guy who needs to be set up with multiple actions to be able to score consistently. He's decent at a number of things at the college level, but I'm struggling to identify a bonafide NBA skill. He has decent IQ, but his passes are pretty rudimentary. He's not going to defend like Royce O'Neale. He's not going to score and get fouled like Alec Burks. He's not going to blow by defenders or defend like Dante Exum. Like most players, his ceiling will be based on how well he shoots the ball, and his shooting last year was so-so.
I think he's most likely to be a bench player. If the Jazz retain Exum, then Allen will be our 4th guard at best, competing for minutes with Burks and Royce O'Neale. Who knows if he'll get time at the 1. Maybe he'll replace Raul Neto.